<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			//1数值
			
			var a = "123";
			var b ="456";
			document.write(a+b);
			document.write("<br/>");
			var num1 =parseInt(a);
			var num2 = parseInt(b);
			document.write(num1+num2);
			document.write("<br/>");
			
			//isNaN判断是否是数字
			document.write(isNaN('abc'));
			
			document.write(isNaN('123'));
			document.write("<br/>");
			
			
			//isFinite()判断是否有限
			document.write(isFinite(1/0));
			document.write(isFinite(1));
			
			//字符串
			//eval()计算字符串的表达式的值  执行js代码
			var a=10;
			var b=20;
			var str = "alert('hello'+(a+b))";
			eval(str);
			
			var str1 = "http;?//";
			document.write(str1);
			var str2=encodeURI(str2);
			
		</script>
	</body>
</html>
